While diplexer coupling elements have appeared in the prior art in various forms, they have lacked the simplicity of the present device. One popular approach in the prior art, is to use a piece of coaxial cable from the common input point to a separate coupling probe or loop. The coaxial cable is configured in substantially one-quarter wavelength of the frequency to be coupled while the coupling actually takes place between the loop or probe and the first resonator element in the filtering device. The adjustment of the loop or probe for coupling with the resonator element was difficult to optimize.
The present invention overcomes deficiencies of the prior art by combining several functions of the prior art into a unitary device which acts as an input signal dividing means, a transmission medium, and a phase adjusting and coupling means. The design is such that the element can be deformed to adjust the average or effective distance between the element and the nearest associated resonator means to optimize the coupling and thus, the tuning and efficiency of the filter apparatus.
It is accordingly an object of the present invention to provide an improved and more cost effective diplexer coupling device.